The present disclosure relates to a switchboard and, more specifically, to a switchboard to which a bushing-type current transformer having a metering current transformer and a metering current transformer bushing is applied.
Generally, a switchboard is a device used in monitoring, controlling, and protecting an electric power system, several electric devices such as a circuit breaker and a current transformer are accommodated in the switchboard to operate or control a power plant and a substation and to operate a motor.
From among the electric devices accommodated in the switchboard, maintenance is able to be performed on those mounted on the front surface portion thereof from a direction of the front surface thereof, but maintenance is difficult to be performed on those mounted on a rear surface portion thereof unless a maintenance space having a particular or larger portion is ensured between the rear surface portion of the switchboard and a rear surface wall or a worker enters the switchboard through the front surface portion thereof.
FIG. 1 is a view illustrating a structure of compartments of a switchboard according to related arts when a circuit breaker is located at a test position, FIG. 2 is a view illustrating a structure of compartments of a switchboard according to related arts when a circuit breaker is located at an operation position, and FIG. 3 is a perspective view illustrating the inside of a circuit breaker chamber and the inside of a voltage transformer chamber of a switchboard according to related arts.
A switchboard applies a voltage and electric current while accommodating several sorts of devices therein and detects abnormality when a fault voltage or current occurs thereby blocking a circuit breaker or providing information to other control devices.
A plurality of compartments are provided in a switchboard so that spaces for accommodating the devices may be defined for each use, and each of the compartments should have shielding and insulating functions that are prescribed under laws and regulations.
The compartments of a switchboard may include a circuit breaker chamber 1 for accommodating a circuit breaker 6, a cable chamber 2 into which a input/output bus or a cable is introduced, a bus bar chamber 3 through which a bus bar passes, a voltage transformer chamber 4 for accommodating a metering voltage transformer, and a low voltage device chamber 5 for accommodating a low voltage device.
Here, each of the compartments, frames, and electric devices or internal components in the compartments are generally coupled to each other through a coupling technique using bolts.
Electric devices accommodated in a switchboard include a circuit breaker 6, a metering voltage transformer 7, a metering current transformer 8, a bus bar chamber bus bar 9, a cable chamber bus bar 10, a metering voltage transformer bus bar 11, a switchboard terminal 12 that is coupled to a bus bar and may be connected to the circuit breaker, a circuit breaker tulip-type terminal 13, and a input/output handle 14 transferring a circuit breaker body.
In the switchboard, as illustrated in FIG. 1, when the circuit breaker 6 is accommodated at a test position in the circuit breaker chamber 1, an electric current is not applied between a power supply and a load. On the other hand, in the switchboard, as illustrated in FIG. 2, when the circuit breaker 6 is located at an operation position, an electric current and voltage may be applied between a power supply and a load, and thus an electric current may be connected or disconnected by the circuit breaker.
The circuit breaker 6 is moved to a test position or an operation position by a input/output handle 14.
When the metering voltage transformer 7 is accommodated in the testing position, a voltage is not detected, as illustrated in FIG. 1. When located at the operation position, the metering voltage transformer 7 may detect a voltage by contacting a switchboard terminal 15 coupled to the metering voltage transformer bus bar 11, as illustrated in FIG. 2.
A method of moving the metering voltage transformer 7 to the test position or operation position may be the same as the method of moving the circuit breaker.
Referring to FIG. 3, side surface frames 16 are symmetrically disposed at both sides of the circuit breaker chamber 1 and voltage transformer chamber 4. A top plate rear surface 17, a top plate front surface 18, a middle base 19, and a bottom plate 20 are coupled to the side surface frames 16 from top to bottom. At a side of a rear surface, an upper rear plate 21, a middle rear plate 22, and a lower rear plate 23 are coupled to pillar frames 24 disposed at left and right sides. A circuit breaker chamber bushing terminal 26 and a voltage transformer chamber bushing terminal 27 are coupled to each of the rear plates 21, 22, and 23 and the pillar frames 24, and a circuit breaker chamber shutter 28 and a voltage transformer chamber shutter 29 are fixed to the pillar frames 24 in front of each of the bushing terminals. These shutters 28 and 29 are opened by a unit connected thereto when the circuit breaker 6 and metering voltage transformer 7 move to the operation position.
One or more front doors 28a, 28b, and 28c may be disposed at the switchboard. The front doors 28a, 28b, and 28c may include a low voltage device chamber door 28a, a circuit breaker chamber door 28b, and a voltage transformer chamber door 28c. A hinge shaft is disposed at one side of each of the front doors 28a, 28b, and 28c, and a handle and a locking unit are disposed at the other side thereof, so that the doors may be opened and closed. The front doors 28a, 28b, and 28c are usually provided so as to manage devices that require much maintenance or front-side maintenance, such as a circuit breaker, a voltage transformer, and a low voltage device that need to be input and output.
Rear doors 29a and 29b are mounted on the rear surface of the switchboard, and usually provided so as to enable to perform maintenance on the metering current transformer and the like that are difficult to be disposed in the front surface portion thereof. Here, a space needed for maintenance should be ensured to open the rear doors 29a and 29b. 
For example, a device attached to the cable chamber 2 or bus bar chamber 3 is shaped such that maintenance may be performed only through the rear surface thereof, and therefore a work space for maintenance should be ensured at the rear surface of the switchboard.
That is, in a switchboard installation space, a front side pathway for the maintenance of a device disposed at a front surface portion with respect to the switchboard and a rear side work space for the maintenance of a device disposed at a rear surface portion should be respectively ensured.
However, a switchboard according to related arts may require a large installation space to ensure both a front side pathway and a rear side work space, and the installation thereof may be difficult when a space for installing a switchboard is limited.